1. Field of the Invention
The present invention relates to an ejector pump for an automotive vehicle fuel tank and more specifically to an ejector pump provided within a saddle-shaped fuel tank to feed fuel from a subchamber to a main chamber. Here, the ejector pump is a kind of pump for jetting a pressurized . water (fuel) through ,a nozzle to eject water (fuel) around the nozzle which uses no moving elements.
2. Description of the Prior Art
There exists a fuel tank provided with a fuel reverse flow prevention device for preventing fuel from flowing in the reverse direction from the fuel tank to the outside through a return tube, as disclosed in Japanese Published Unexamined (Kokai) Utility Model Appli. No. 59-190628. In this prior-art fuel tank, the fuel reverse flow can be prevented by providing an air chamber formed with a port communicating with a space within a tank at an end of the return tube at such a position that the end of the return tube is located in a space within the air chamber when the vehicle is overturned.
On the other hand, there exists a saddle-shaped fuel tank for an automotive vehicle, which is formed with a middle raised bottom portion extending from the bottom wall of into the tank. This saddle shape is required structural restriction of the vehicle body in which which the fuel tank is mounted, as disclosed in Japanese Published Unexamined (Kokai) Patent Appli. No. 61-65067. In the above-mentioned fuel tank, the fuel tank is partitioned by a raised bottom portion into a main chamber and a subchamber at roughly the lower half level within the tank body. When the liquid level drops below the raised bottom portion within the fuel tank, it is necessary to transfer fuel from the subchamber to the main chamber within the fuel tank by an ejector pump attached to an end of a return pipe for returning excessive fuel supplied to the engine into the fuel tank again. The more detailed description of the saddle-shaped fuel tank provided with an ejector pump will be made under DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS with reference to FIG. 1.
In the above-mentioned saddle-shaped fuel tank provided with the ejector pump, however, since an ejector operation is effected owing to the fuel recirculated through the return pipe, there exists a problem in that it is impossible to provide a fuel reverse-flow prevention device (i.e. an air chamber) as disclosed in the former Kokai Appli. No. 59-190628 at an end of the return pipe.
Although it may be possible to provide a fuel reverse flow prevention device of different type for the saddle-shaped fuel tank, in this case there arise various problems for example, in that the number of parts increases, the tank capacity decreases due to the presence of the prevention device and the manufacturing cost becomes high.